InternalCurrentPatterns.ppt
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1、1,Specialized English,School of Physics & Optoelectronic Engineering W. Zhang,电子科学与技术专业英语 ,2,电子科学与技术专业英语 ,2.1.3 Internal Current Patterns,3,电子科学与技术专业英语 ,A detailed examination of current components in the biased BJT reveals a relatively complicated pictureFortunately,there exist approximations that
2、are simple and yet quite accurate through wide ranges of conditions. This is another way of saying that some of the most complicated features of the device are often small enough to be neglected safely.,偏压晶体管的电流分量的精确测量给出了一个相互影响的复杂的电流图。幸而,所存在近似电流通过宽的区域范围是比较简单且非常精确。另外一种说法是器件复杂的特点的电流通常小的确实可以忽略。,4,电子科学与
3、技术专业英语 ,Figure 2-4 is a physical representation of a BJT in the ”common-emitter orientation“ shown first in Figure 2 - 1(a) . The large primary arrow directed from collector to emitter is identically , representing one-dimensional electron transport. The labels IC and IE show that it constitutes bot
4、h the collector-terminal current and the emitter-terminal current, which typically differ by only about one percent,图24是首次在图21(a)给出了共发射极取向晶体管的物理描述。从集电极到发射极的大的原始箭头同一方向的,代表了一维情况下电子传输方向。标识IC和IE分别代表集电极端和发射极端的电流,且它们的区别只有1。,5,电子科学与技术专业英语 ,Shown also are other current “strands” that depart from the primary
5、 current or join it. The relative magnitudes of the secondary currents are represented qualitatively by their widths, but for clarity all of these widths are grossly exaggerated with respect to that of the primary arrow.,同时也给出了从原始电流出发或加入的电流的其它电流部分。二级电流的相应值定性用宽度表示,但为了区分所有宽度我们通过相对于原始电流箭头宽度来按比例确定。,6,电子
6、科学与技术专业英语 ,The circled values give typical currents one might encounter in a small BJT (a “milliwatt device“) under bias, and it is evident that they differ by many orders of magnitude.,相关电流值给出了发生在一个小型偏压晶体管(毫瓦器件)的典型电流,显然它们有数量级差异。,7,8,电子科学与技术专业英语 ,The most important of the secondary currents is the o
7、ne labeled IB, the base-terminal currentIt differs in numerous and major ways from the primary electron current that has occupied us up to this point:First it is a majority-carrier current,or a hole current in the NPN device. Second,it flows laterally from the base contact into the active region of
8、the BJT,最重要的二级电流是基极端电流IB。它在数量级和流动主要方式不同于原始电流,原因在下述几点:首先,它是主要载流子电流或在NPN器件的空穴电流。第二,它是横向从基极向晶体管的活动区域流动。,9,电子科学与技术专业英语 ,Refer back to Figure 22, which shows the commonplace (diffused) BJT in a relatively realistic cross section. The portion of the base region contiguous with (or “under“) the emitter reg
9、ion is the active base region, sometimes also termed the intrinsic base region(This use of the term does not have doping connotations),回到图22,图中给出了在实际中截面区域的常见(扩散)晶体管。接触发射区基区连接端是一个活动的基极区域,有时也认为是本征基极区域。(在实际能级应用中不具有掺杂的特点),10,电子科学与技术专业英语 ,The outer portions of the base region,in analogous fashion,are som
10、etimes designated by the adjective extrinsic It is there that the base contact is made in this kind of BJT(Base contacts,by the way,can be and often are made on both sides of the emitter)The third major distinction of the base current from the primary electron current thus becomes evident,在类似结构中,基区的
11、外接端有时制备成的非本征情况。在这类晶体管通常是基极接触。(顺便说基极接触能够且通常可做在发射极两侧)来自于原始电流的基极电流的第三个主要差异也变得显著。,11,电子科学与技术专业英语 ,The current of holes traverses a relatively long path within the base regionIn the example we are considering it could be several tens of micrometers,as compared to the less-than-one-micrometer base thickne
12、ss traversed by the electrons.,空穴电流在基区传输移动相对较长的距离。 在所给例子中与少于一毫米基区厚度的电子移动相比,我们认为空穴移动有几十毫米。,12,电子科学与技术专业英语 ,Once in the intrinsic base region,most of the holes undergo a change indirection and flow into the transition region of the emitter junctionThis obviously involves a complex current pattern. It
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